Tuning device for wireless receiving circuits



July 1, 1924.

C. M. GRAY TUNING DEVICE FOR WIRELESS RECEIVING CIRCUITS Filed Aug. 15 192] 2 Sheets-Sheet 1 WITNESSES ATTO R N EY Patented July 1, 1924.

"UNITED STATES COLEMAN MULFOBD GRAY, OF DEL MAR, CALIFORNIA.

TUNING DEVICE FOR WIRELESS RECEIVING CIRCUITS.

Application filed August 15, 1921. Serial No. 492,385.

T 0 all whom it may concern.

Be it known that I, COLEMAN M. GRAY, a citizen of the United States, residing at Del Mar, in the county of San Diego and State of California, have invented new and useful Improvements in Tuning Devices for Wireless Receiving Circuits, of which the following is a specification.

This invention has reference to tuning devices for radio or wireless telegraphs, and its object is to provide tuning means of great delicacy and far more reliable in action than is customary, the action of the instrument being similar in minuteness of adjustment to that of a vernier in conjunction with linear measurements, while retaining some of the features of the radio instrument known as the variometer.

In'accordance with the invention, there is provided a fixed coil in which there is mounted a movable coil rotatable in the axis of the fixed coil, and within the movable part and rotatable about the same axis as the latter there is mounted still another coil which may participate in the movements of the second coil, or have .a range of movement independently of the second coil. The arrangement is such that either the inde endent or the unison movement of the thir coil makes it possible to produce variations in effect of great minuteness, by-

advancing or retarding adjustments of the third coil with respect to the second coil and also with respect to the fixed coil.

The invention is based in part upon the instrument known as the variometer and extensively used in radio circuits of all types, as sending, receiving, measuring, etc. v The variometer usually consists of two coils, concentrically mounted and connected in series. The external coil, called the stator, is stationary, while the internal coil 'or rotor, is rotatable through an arc of 180. When the rotor is at one end of its travel, the direction of its winding is opposed to the winding of the stator and the inductance is at a minimum. When the rotor is at the other end of its travel, the direction of its winding is that of the stator, and .the inductance is at a maximum. At any intermediate position, theinductance will be a function of the angle of rotation. It is usual to wind both the stator and the rotor on spherical forms to thereby provide a minimum clearance between the two, and to employ a fairly large number of turns of winding. Both of these forms of construction are necessary if the variometer is to cover a sufficiently broad band of inductance to render it useful as a tuning device.

The variometer, as described, forms one of the most delicate variable tunin devices heretofore known, and is further esirable in that it eliminates certain. losses found in other types of variable inductances which need not be here described. However, since the introduction of continuous wave transmitting apparatus operating at very high frequencies (short wave lengths), it has been found that even the variometer as usually constructed does not permit of sufficient delicacy of adjustment to give satisfactory tuning. If the variometer contains a large number of turns, its tuning range will be broad, but its adjustment will be coarse. If it contains a relatively small number of turns the adjustment will be fine, but the tuning range is then impractically small. A' possible solution of this condition is to place two variometers, one large and one small, in series but this brings about a needless complexity of apparatus and often presents undesirable electrical features.

The present invention, comprising a variometer with vernier adjustment, presents a completely satisfactory solution of the problem. It consists of a standard variometer with a third coil, also rotatable, placed inside of the rotor and in inductive relation to it.

This third or Vernier coil is mounted on the same centers or axis as the rotor and may be turned with the rotor or turned while the rotor remains stationary. The Vernier coil need contain but a relatively small number of turns so that a large rotation of this coil with respect to the rotor creates but a small change in the total in-- ductance of the device. The principle of this vernier coil with respect to the rotor coil is the same as that of the rotor coil with respect to the stator coil. When the rotor and Vernier coils lie in the same direction, inductance is at a maximunnand when they lie in opposite directions, the inductance is at a minimum, while at any intermediate point the inductance will be a function of the angle'of rotation.

The invention willbe best understood from a consideration of the following de tailed description taken in connection with the accompanying drawin' s forming a part of this specification with t e understanding, that the invention is not confined to any strict conformity with the showing of the drawings but may be changed and modified so long as such changes and modifications mark no material departure from the salient features of the invention as expressed in the appended claims.

In the drawings:

Figure 1 is a diagrammatic perspective view of the invention with the coils displayed.

Figure 2 is an end view of the structure of the invention. 1

Figure 3 is a cross section on the line 3-3 of Figure 2.

Figure 4 is asection on the line 44 of Figure 2.

Referring to the drawings, as shown in Figs. 2, 3, and 4, two blocks 1, 2, respectively, which ma be made of wood or other suitable materia, are indicated as of rectangular outline. These blocks together constitute the body of the instrument and each block has a cavity 3 in one face of partially spherical form. Laid within each cavity 3, in close conformity with the cavity, is a coil 4 of wire, preferably held in place by some suitable cementitious material restraining the coil from disturbance and constituting a lining for the blocks 1 and 2. The coils 4 are connected togetherintermediate of their lengths by a bridge wire 5 so that the coils are electrically in series. One end of one of the coils is connected by a conductor 6 with metallic strips 7 leading across the space between the two blocks and serving, in conjunction with another such strip 8 on the opposite side of the instrument, to hold and anchor the two blocks 1 and 2 together.

Lodged within the cavities 3 but spaced concentrically from the inner walls thereof,

is a spherical body 9. This body is hollow with an equatorial rib 10 and truncated polar extensions 11. The exterior of the spherical body 9 is provided with a spherical winding 12, concentric with the windings 4 in the blocks 1 and 2,.but these windings 4 and 12, though spaced apart in order to avoid mechanical contact, are within induc tive range. The winding 12 extends from the rib 10 to the extensions 11.

The body 9 with the windings 12 constitute the rotor of the apparatus and corresponds to the movable variometer wind ing of the ordinary variometer structure.

Extending from diametrically opposite sides of the rotor 9 are axles 13 in the form of metal tubes projecting through the intermediate spaces between the blocks 1 and 2, and journaled in the strips 7 and 3, which latter are provided with longitudinal slits 14, permittingthe strips 7 and8 to grip the l I neeaeve hollow axles 13 with suficient force to provide such 'frictionalcontact with the axles as to hold them and the rotor 9 in any position of adjustment, but not offering suliicient mechanical resistance to preventmanipulation of the rotor 9 by thetfingers-of the operator, the rotation of'the rotor being facilitated by a knob or manipulating wheel 14 at one end of oneof the axles 13.

Extending through each axle 13, which is hollow, is a sleeve or tube 15 of insulating material also extending beyond the inner end of the respective axle 13. The sleeves or tubes 15 are axially traversed by rods 16, 17, respectively projecting into the interior of the hollow rotor body 9, the rod 17 also projecting beyond the knob 14 and carrying another knob or manipulating wheel 18, whereby the rod 17 may be turned.

Carried by the rods 16 and 17 and extending between their inner ends within the rotor 9 is a coil 19 composed of asuitable sleeves 15 is insufiicient to carry the coil 12 and the supporting body 9 with them.

The terminals of the Vernier coil 19 are connected by conductors 20 to the ends of the rods 16 and 17 one of which is in turn connected to a journal bearing 21 in the form of a terminal strip 22 from which current may be taken. The coils 4 are coupled up in series and at one end are connected by a conductor 23 to the terminal 22, while at the other end the same coils 4 are connected by the conductor 6 to the bar 7.

The stator coils 4 are connected together by the bridging conductor 5 while the coils 12 of the rotor of the variometer member are connected together by conductor25, so as to be in series with each *other' and are connected up by conductors .24 to the respective axles 13.

In the particular model of the invention shown in the drawings, the current may be considered as first passing through the outside or stator winding, then through the rotor winding and then through the Vernier winding and finally through the inside or second shaft 16, 17, which is insulated from the first or hollow shaft 13 by the insulating bushing 15. The Vernier shaft forms a steady and extended bearing for the Vernier winding, which it carries, and from which connections may be made to other pieces of apparatus. f

The manipulating or control buttons 14 and 18 for both the main rotor and the vernier rotor are, for convenience, located on the opposite side of the instrument from where the current is taken from the Vernier winding. The hollow shaft of the main rotor carries one control button for the coarse adjustment of both the movable windings. The frictional contact between the shafts causes their common movement, when w so desired, or individual'movement of the vernier winding, and when the Vernier winding is alone adjusted the outer or stator winding and the main rotor winding remain stationary.

It is contemplated, though not so shown in the drawings, to provide suitable dials and indicating arrows attached to the respective parts of the stator housing and the main rotor shaft, and also to the main rotor 20 shaft and the vernier shaft, so that the angular positions of each winding to its adiacent winding may be observed.

uitable means for obtaining proper friction between the shafts, such as the custommy adjustable pinch binds, set screw, etc., may be employed, but are so common in practice that illustration thereof is not deemed necessary.

It is to be understood that three coils mounted on cylindrical or spherical forms are not the only embodiments of the invention, or the only manner in which the ver-' wider principle may be employed, for such form has simply been selected out of many posible forms fomthe purpose of demonstration, since the spherically wound type is the most usual variometer in use at present. As a matter of fact the windings may be helical, spiral, toroidal, or of other form as embodying the principle of vernier adjustment of the variometer, so long as such adjustment remains the same whatever form of winding be adopted, and which windings may be brought into inductive relation with as each other.

Nor is it intended that the invention be restricted to a single vernier winding as representing the only possible construction, for it is entirely feasible to use any number of vernier windings to secure varying steps of inductance for particular purposes.

' For the purpose of demonstrating the value of the invention, reference has been made to the reception of continuous-wave radio signals of very high frequencies, but this is not to be taken as the only manner in which the invention is to be usefully employed. of any type, damped, or undamped, modulated undamped, or telephone will be aided by the proper employment of the invention. By the word reception it is not intended that the invention is for use solely in tuning any particular portion of a as receiver circuit to the exclusion of other por- The reception of radio signalstions, but it is to be understood that it may be used equally well for detection, heterodyning, autodyning, regeneration, amplification, and repeating. Furthermore, while reception is suggested as the most usual employment for such a delicate tuning device, the invention is equally applicable to transmitting circuits of alltypes, the measuring circuits of all types, and in fact for use in any electrical circuit whatever, of whatever nature, in which a continuousl and minutely variable inductance is desire The operation of the invention will be best understood by considering the instrument as composed of three coils, one of which is stationary and the other two of which are collectively or independently adjustable about a single axis: The vernier coil contains a relatively small number of turns in order that a large rotation of the Vernier coil with respect to the movable variometer coil creates but a slight chan e in the total inductance of the device. The relation of the stator and rotor coils in their Ielative movements is such that a full 180 degree rotation of the vernier coil will equal but one or two degrees of rotation of the main rotor, so that the device will permit of the selection of infinitely small values of inductance within the limits of practical breadth. The number of turns of wire on the additional rotor coil or coils constituting the vernier coil is much less than the number on the main rotor so that the rotation of the additional Vernier coil or coils will produce but a minute change in the total inductance of the instrument compared to the rotation of the main rotor.

What is claimed is 1. A device of the character described comprising a fixed coil, a second coil mounted for rotation and arranged in inductive relation to the fixed coil, and a third coil mounted for rotation and having relatively few turns as compared to the second coil, said third coil being arranged in series with the second coil and in inductive relation to it.

2. A variometer comprising a series of associated coils of which one is fixed in space, another is located interior to the first coil and is rotatable about an internal axis transverse to the coil and in inductive relation thereto, and another coil interior to and in series with the second coil and in inductive relation thereto, and rotatable about the same axis either with or independently of the rotation of the second coil.

3. A varic meter comprising a series of associated coils of which one is fixed in space, another is located interior to the first coil and is rotatable about an internal axis transverse to the coil and in inductive relation thereto, and another coil interior to and in series with the second coil and in inductive relation thereto and rotatable about the same axis either with or independently of the rotation of the second coil, all of said coils having a common center of rotation.

4. A variometer comprising a body portion or housing with a fixed coil therein, another coil mounted in the fixed coil for rotation about an axis corresponding to that of the fixed'coil, and another coil within the second coil and in series therewith and mounted for rotation a out the same axis .and related in number of turns to the second coil whereby it exerts a similar efi'ect to the second coil but of a minute amount as compared therewith. f

5. A variometer comprising a plurality of coils, one of which is fixed, another of which is movable with respect to the fixed coil, and another of which contains a relatively small number of turns and is movable with respect to either or both of the first and second named coils, said coils being respectively related so that the second and'third named coils are in series with each other, the second coil is in inductive relation to the first coil, and the third coil is in inductive relation to the second coil.

6. A variometer comprising a fixed outer coil, an interior coil adjustable about an axis diametric of the outer coil, and a vernier coil in series with and interior to said interior coil and adjustable about the same axis as the latter, said vernier coil containing relatively few turns compared with said interior coil, whereby a large movement of the vernier coil has a relatively small effect.

7. A variometer comprising a fixed outer co'il, a second coil interior to the fixed coil and adjustable about an axis diametric thereto, a third coil in series with and interior to the second. coil and adjustable about the same axis as the second coil, and containing relatively few turns compared with the second coil, whereby a large movement of the third coil has a relatively small efi'ect, the second coil being in inductive relation to the first coil, and the third coil in inductive relation to the second coil.

8. A variometer comprising two coils in inductive relation, one of said coils being fixed and the other rotatable about an axis diametric to both coils. a vernier coil adjacent to the rotatable coil, in series with, and

- aeaaeaa means for the rotation of the second coil and its support within the fixed coil, and a vernier coil mounted within the second-named support and in series with the second coil, said second coil and the vernier coil being mounted to rotate about a common internal axis.

10. A variometer provided with an outer fixed hollow coil, an inner adjustable coil in inductive relation to the fixed coil,.and a vernier coil within and in series with the adjustable coil and in inductive relation thereto, the vernier coil having an axis support traversing and frictionally held in the adjustable coil for both conjoint and independent rotation with respect thereto, whereby both coils may be moved together or may be moved independently for producing minutie variations of inductance by the vernier CO1 e 11. A variometer comprising a plurality of coilsall connected in series, one of which coils is fixed in space, another of which is movable with respect to the fixed coil, and another of which contains a relatively small number of turns and is movable with respect to either or both of the first and second coils, said coils being respectively related so that the secondcoil is in inductive rela tion to the first coil, and the third coil is in in ductive relation to the second coil.

12. A device of the character described comprising primary and secondary coils in series in inductive relation and relatively movable to effect a maximum variati: a in the inductance, and a third coil electrically in series with the secondary coil,- said third coil having comparatively few turns and adjustable with respect to the-secondary coil to effect minute corrections in the inductance.

In testimony, that I claim the foregoing as my own, I have hereto aiiixed my signature.

COLEMAN 

